I watched it perhaps around 2008. It was a horror film. In the movie, a group of friends (2 girls and 3 boys maybe) got killed in a remote house probably in woods. They were lured there by an old man who informed them some kind of party was going there in the night. In the party the friends got detached. One friend discovered no body was taking with anybody. Another one discovered some freaky epic weapons which we see in the picture of hell in a room. Later, he was killed by some demon from hell. Only a girl could get out of the house, but I forgot what happened to her.
In the end, it was discovered they were just dreaming. In reality, they were drugged by the same old man, father of one of their friends for whose death they were responsible. He took vengeance by drugging the group and burying them under the soil within a wooden crate. he kept them living by supplying oxygen to the crate via a tube. When somebody was dying in their dream, in reality he was killing himself. Somehow one girl and one boy got saved. Police came and when they tried to arrest the old man, they found him dead in his apartment. This was a color film.